The present invention refers to machines for drilling of the ground.
In particular, the present invention relates to equipment used in machines for the mixing, consolidation and compaction of soil.
Various procedures are known for the consolidation of the ground through the formation of cylindrical columns of consolidated soil, based on the mixing of particles of the soil with legants, usually cemented mixtures.
The traditional procedure, through which a mainly mechanic mixing is carried out, uses the rotating movement of tools able to dig and disintegrate the soil through appendixes which radially extend to the axis of the tool. The soil so disintegrated is kneaded with a low-pressure (1-2 MPa) cemented mixture pumped through openings on the tubular shaft which supports the digging tool.
A known variant of the described procedure is to use higher pressures for the cemented mixtures. This technique, by using a combination of the mechanical action of the disintegrating members of the tool and of the kinetic energy of the pressurized jets, differs for a substantial execution speed, with considerable economic advantages.
FIG. 1 shows a typical machine M normally tracked for the drilling of the ground, which can bear the characteristics of the present invention.
This machine is provided with a vertical tower 2 or antenna along which slides a group 3 for the movement of drill rods commonly known as a “rotary table”.
This motorized group moves along guides 21 of the tower and is hung on one or more traction and thrust handling devices (i.e.: hoists). Traction can be direct or multiplied (typically multiplied by two or four). The rotary table is hydraulic and transforms the energy provided by a pressurized fluid into mechanical energy. One or more hydraulic motors give rotary movement to one or more gears coupled to a crown. In the center of the crown is a flanged sleeve 31 provided with internal vertical listels 32, normally three or six, imparts rotation to a cylindrical rod, which also has external listels. The listels of the sleeve contact with the listels of the cylindrical rod making this last in the movement of rotation.
When the cylindrical rod is provided with external listels for transmitting movement or if it extends at least partially over the “rotary table”, it is commonly called a tube 4.
In the bottom part of the tube is fixed the first of the rods of battery 5. Each rod is fixed to the following one with a joint having many shapes, screwed, flanged with screws or locked through pins.
The last rod bears in its lower part digging tool 6.
The tube is therefore a fundamental part of the machine because it receives the traction torque and the thrust of the rotary table and transmits the torque and thrust to the rods and conveys at the same time the pressurized fluid in direction of the digging tool.
The digging fluid is typically a consolidating fluid, generally a cement mixture, chemical mixture or concrete.
Trying to increase the depth of the excavation, it has been thought that the length of the tubes of traditional type should be increased.
In this light, it has been realized the possibility of stopping at various levels of the tube the rotary table, by inserting coupling and supporting points 41. In this way when the rotary is at the lower limit switch with respect to the guides of the tower, the tube can be inserted in the ground for several meters in such a way as to achieve treatment depths deeper than the length of the tower (typically up to 8-9 meters).
In order to face the extension of the tube, a rudder 7 is mounted which has the function of blocking the rotation of the fixed part of the cement grout feeding head 8 mounted on the top of the tube. In the absence of this accessory, the rubber pipes of the feeding of the treatment fluid would wind around the tube at every turn of the rod. The rudder is therefore an indispensable element, even if extremely not easy to handle and is also generally stressed by heavy oscillations when the rotation speed of the rotary acquires high values.
The technology and the available materials cautiously suggest not using too long tubes, having for example length higher than 8-9 meters, as this may affect the stability of the machine.
A kind of tube is described in patent application TO2004A000457 which refers to a continuous propeller ground drilling tool having an extension rod provided with at least two coaxial extensions, which moving between them, determine a fictitious extension of the drilling. They are connected at the bottom side to the propeller battery and have a propeller in the most external element.
This system actually permits a relative displacement between the two sliding elements but with an encumbrance in length equal to “x”, permits an extension of the drilling equal to the encumbrance itself, that is equal to “x”. The relative movement between the parts has the only function of moving the propeller in a more suitable position for generating the hoisting of the ground caused by the spirals and does not increase the drilling depth.
Furthermore, the document US2008/2170037 describes a machine provided with a telescopic tube which comprises at least two extended coaxial elements and reciprocally extractable. The tube extracts proportionally to the movement of the carriage which supports it and slides on the antenna.
It is to be noted that there is not a passage of pressurized fluid through the elements of the tube.
The present invention proposes a machine for drilling of the ground provided with a telescopic tube able to substantially increase its length (for example by doubling it at a value equal to approx. 2 times “x”), without losing the abovementioned characteristics of torque transmission, traction/thrust and above all the conservation of the pressure of the fluid which flows inside them.